Linux

If the drive previously wasn't making this noise (as in it had been filled with data, been in use for days-weeks and wasn't ever making this noise) and it doesn't happen in response to data writes (even hours after the fact) then it might be a cause for concern that the drive could be dying.

In general it's a good idea to have back-ups of any important data but I'd really ensure that's the case here and assume it could imminently fail. In general the sound of hard drives changing (that is sounding different in either idle noises or active writing/reading noises) is a cause for concern for potential drive failure though it could be other things and as drives age they can sometimes change sound signatures as mechanical components age without necessarily failing (could go on working fine for years).

That said there are normal processes in drives that can make noise:

• Some sort of operation driven by your OS itself, I won't begin to get into all of them but there could be something accessing things in the background, doing file table or journaling operations, writes, checks, etc on the file system itself, just low level maintenance stuff.

• SMR drives may continue to write and shuffle data for quite some time after being written to, especially if it was a large amount of data. Though this should still even in the case of multiple terabytes probably be resolved within 12 hours.

• Many drives, especially high capacity enterprise drives do make a -soft- clicking sound as a result of the arms sweeping the surface when idle but not off to if I recall correctly spread around lubricant or some sort of basic mechanical maintenance. It's part of the normal drive operations. It's possible it occurs more frequently in response to a massive amount of writes previously like filling a drive or may not be activated until a certain amount of data is written, I'm not really sure how that works as that would probably be proprietary information to the manufacturer.

Should I be worried about this? To my paranoid mind it feels like something is slowly reading my files with some exploit to bypass the indicator light to fly under the radar.

How would it do this? Is it installing hacked firmware to your enclosure too? I doubt you're that valuable of a target.

If you're worried about malware then back up your stuff, nuke the install and reinstall from scratch. I wouldn't worry about it if this is the only thing you're seeing and find it unlikely.